The 3rd Generation Partnership Project (3GPP), which is a standardization project, has standardized the Evolved Universal Terrestrial Radio Access (EUTRA), in which high-speed communication is achieved by adopting an Orthogonal Frequency-Division Multiplexing (OFDM) communication scheme and flexible scheduling on a given frequency and time basis called a resource block. EUTRA is also referred to as Long Term Evolution (LTE), in some cases.
Moreover, in 3GPP, Advanced EUTRA. (also called LTE-A) for enabling higher-speed data transmission and having upper compatibility with EUTRA is studied.
In Advanced EUTRA, the introduction of direct communication between terminal devices (Device to Device (D2D)) is considered. In D2D, as services between terminal devices in close proximity to each other (Proximity based Services (ProSe)), a scheme to confirm (discover) whether the terminals are positioned in close proximity to each other (also called ProSe Discovery, D2D Discovery, or Sidelink Direct Discovery), a scheme by which the terminal devices perform data communication therebetween without passing through a base station device (also called ProSe Communication, ProSe Direct Communication, D2D Communication, D2D Direct Communication, or Sidelink Direct Communication), and the like are specified (see NPL 1), and further functional extensions are studied.
For example, schemes that are studied include a scheme for enabling the transmission (Sidelink Direct Discovery announcement), the reception (Sidelink Direct Discovery announcement monitoring), and the like of Sidelink Direct Discovery, even in an area outside the coverage of the network, even at a different frequency, even in an area of another Public Land Mobile Network (PLMN), or the like, and a scheme for enabling a terminal device at an coverage end of the network and a terminal device in an area outside the coverage, or the like to be connected to the network through communication by D2D with a terminal device inside the coverage of the network (see NPL 2 and NPL 3).